<!DOCTYPE html>
<html lang="en" class="reftest-wait">
<meta charset="utf-8">
<title>Starting to scroll the nested scrollbox shouldn't invalidate the fixed layer</title>

<style>

.content {
  box-sizing: border-box;
  width: 200px;
  height: 200px;
  border: 1px solid black;
}

.fixed {
  position: fixed;
  top: 20px;
  left: 240px;
}

.reftest-no-paint {
  border-color: lime;
}

.scrollable {
  overflow: auto;
  padding: 10px;
}

.scrolled {
  border: 1px solid gray;
  height: 400px;
}

body {
  margin: 0;
  padding: 20px;
  height: 3000px;
}

</style>

<div class="scrollable content" id="aboutToScroll">
  <!--
    This scrollbox starts out without active scrolling and is going to become
    actively scrolled.
  -->
  <div class="scrolled"></div>
</div>

<div class="fixed reftest-no-paint content">
  <!--
    This fixed layer gets its own PaintedLayer above the rest.
    When the contents of .scrollable require their own PaintedLayer, that
    should not cause .fixed to change layers.
  -->
</div>

<script>

function doTest() {
  document.querySelector("#aboutToScroll").scrollTop = 50 - document.querySelector("#aboutToScroll").scrollTop;
  document.documentElement.removeAttribute("class");
}
document.addEventListener("MozReftestInvalidate", doTest, false);

</script>
